H-6 Fuses And Breakers

Question 1

What is overload protection ?

Answer 1

overload: A moderate increase in current to an above normal level over a short period time .

Question 2

What is over current ?

Answer 2

overcurrent : A current much larger then normal , momentarily

Question 3

One advantage and one dis advantage of a fuse

Answer 3

Faster , more reliable , Only used once

Question 4

One advantage and one dis advantage of a breaker

Answer 4

resetable, may have poor repeatability

Question 5

two injurious effects that short current causes

Answer 5

mechanical , thermal stress

Question 6

What determines how much current flows through when a fault occurs

Answer 6

IMPEDENCE

Question 7

A fuse with HRC means

Answer 7

HIGH RUPTURING CAPACITY (FAST)

Question 8

maximum current for plug fuse

Answer 8

30 A

Question 9

Max voltage rating for plug fuse

Answer 9

150v to ground

Question 10

2 other reasons a fuse may open

Answer 10

High Ambient temperature , vibrations , poor connection

Question 11

what do “tamper resisting” plugs do ?

Answer 11

Prevent overfusing

Question 12

Name 2 different style of cartridge fuses

Answer 12

Bolt on , ferrile , blade

Question 13

A fuse is marked with the letter d

Answer 13

Marked as TIME DELAY

Question 14

Example of a fast speed response fuse

Answer 14

Electronics - fast

Question 15

Example of a slow speed response fuse

Answer 15

Breakers - motor protection

Question 16

significance of the voltage rating in fuses

Answer 16

Maximum voltage fuse may operate at

Question 17

significance of continuous current rating in fuses

Answer 17

Maximum current fuse may operate at

Question 18

Significance of interrupting capacity

Answer 18

Maximum fault current fuse can handle without destroying itself

Question 19

A fuse is marked with the letter P

Answer 19

Marked as LOW MELTING POINT

Question 20

Max current ratings for cartridge fuses

Answer 20

600A

Question 21

Max voltage ratings for cartridge fuses

Answer 21

600V

Question 22

One adv , one disadv of “One Time” and “Renewable” cartridge fuses

Answer 22

Used One time ,cant tamper with fuselinks

renewable , can be spiked

Question 23

What is meant by the term code fuse

Answer 23

Class H (10 000 AIR)

Question 24

Maximum interrupting rating for code fuses

Answer 24

10 000A

Question 25

What is a dual element fuse ?

Answer 25

Two elements , protecting against shorts and overloads

Question 26

Cartridge Fuse

Answer 26

Ferrule - contacts , knife , bolt on

Question 27

Type C fuses :

Answer 27

Rejection Ring must be used

Question 28

Type S fuses :

Answer 28

Rejection adapter must be used

Question 29

Standard low voltage ratings for Fuses

Answer 29

125v , 250v , 300v , 600v

Question 30

What kinda base does a plug fuse have?

Answer 30

Screw Base , Edison Base

Question 31

What does a fuse do?

Answer 31

Protects the Conductor in a circuit

Question 32

How does a Bi metallic fuse work ?

Answer 32

An insulated tube containing metal strips that melt if too much current passes through ( short circuit )

Question 33

Are type C AND S interchangeable?

Answer 33

NON INTERCHANGABLE

Question 34

Proper voltage rating is required ...

Answer 34

To prevent the arc from re striking.

Question 35

What do the letters HRC mean when refering to a fuse ?

Answer 35

High Rupturing Capacity

Question 36

What is the essential difference between HRC1 AND HRC2 fuse ?

Answer 36

HRC2 Does not protect against overload , it is used with overload heatres

Question 37

what is a rejection holder?

Answer 37

Rejects a standard H fuse

Question 38

Usual interrupting capacity of HRC fuses

Answer 38

200 000A

Question 39

What is difference about HRC fuses then cartridge fuses ?

Answer 39

Silver links ( lower resistance) , ceramic body , sand filler

Question 40

Are HRC1 AND HRC2 fuses interchangeable ?

Answer 40

No

Question 41

Does code let HRC fuses be used instead of cartridge fuses

Answer 41

Yes

Question 42

what are HRC1 used for

Answer 42

General Purpose Motors

Question 43

HRC2 is used for what?

Answer 43

Motor circuits that use seperate overload protection

Question 44

Explain Trip Free

Answer 44

The breaker cannot be held ON . It is free to trip.

Question 45

Explain Thermal Trip

Answer 45

Trips on bending bi metallic strip ( time delay )

Question 46

Explain Magnetic trip

Answer 46

Taps in magnetic Coil

Question 47

Explain Thermal - magnetic trip

Answer 47

combination of metal strip and magnetics.

Question 48

what do the letters GFCI mean?

Answer 48

Ground fault circuit interrupter

Question 49

If a two pole breaker is not available , it is permissible to use a two single pole breaker?

Answer 49

Yes, as long as the poles are together using a tie bar